/**
  * This method submits the receipt transaction list to MasterCard as a final step
  * in the Wallet process.
  *
  * @param Transaction $transaction
  *
  * @return string The XML response from MasterCard services
  */
 public function postTransaction(Transaction $transaction)
 {
     $xmlTransaction = $transaction->toXML();
     $params = array(Connector::OAUTH_BODY_HASH => $this->connector->generateBodyHash($xmlTransaction));
     return $this->connector->doTransaction($params, $xmlTransaction);
 }